There is an effort to capture digitized values based on a radiograph for medical diagnosis, and to subject the values to imaging process for generating an image that is more suitable for diagnosis, and to reproduce the image by exposing using a laser beam.
With a scanning technique, where main scanning is based on a laser beam, and sub-scanning is based on mechanical shifting means, accuracy of scanning speed both in main- and sub-scanning directions is limited, and this limitation results in density irregularities, i.e. scanning-induced density irregularities, once a silver halide photographic light-sensitive material is processed to obtain an image, thereby the resultant image may be jeopardized and may lead to a wrong diagnosis.
One method to solve such a problem is to make contrast .gamma.=1.0 to 2.5, preferably, 1.7 to 2.2, relative to a range 1.0 to 2.0 of the transmittance density D ##EQU1## of the above-mentioned silver halide light-sensitive hotographic material undergone developing. This method is capable of making scanning induced density irregularities less visible. Accordingly, a silver halide light-sensitive photographic material satisfying relevant conditions incorporates, for example, a silver halide emulsion whose average grain size being 0.1 to 0.7 .mu.m.
However, developing a light-sensitive material containing silver halide grains of the average size above may turn the tone of developed silver yellower, and the possible reason of which is that around a silver image occur ultra-fine colloidal silver grains that have failed to satisfactorily grow into silver filaments, thereby the silver image appears yellowish due to light diffused by these silver grains.
For tone improvement on a silver image, studies were performed with various tone improving agents, and one effective such an agent is a mercapto compound. A mercapto compound, for example, 1-phenyl-5-mercaptotetrazole is known to be effective in improving tone. However, using a large amount of such a compound in order to sufficiently improving tone results in loss in both maximum density and sensitivity (Japanese Patent Publication Open to Public Inspection, hereinafter referred to as Japanese Patent O.P.I. Publication, Nos. 111846/1981 and 71047/1984).
In order to reduce density irregularities mentioned above, lowering gradation of a light-sensitive material is a usual practice. However, excessively low gradation makes it impossible to provide sufficient exposure of a laser beam, thereby a low density image can only be obtained, may result in inhibiting diagnosis.
The light-sensitive material of the invention is exposed using a laser beam. For this purpose, a He-Ne laser is particularly advantageous because of stableness in performance, durability and the like. A latent image generated by exposing in a short duration with highly intense laser beam is readily affected by change in developing conditions such as a processing temperature, time, and stirring conditions, and may cause density irregularities in photographic processing.